Determination of magnetic field effects on a jet diffusion flame in a microgravity environment

Abstract

The effect of magnetic fields on a laminar jet diffusion flames has been investigated by using a microgravity environment. The magnetic field was changed from fairly low (around 0 mT) to strong (around 215 mT) intensities. The effect of oxygen concentration was also investigated. The buoyancy caused by gravity is dominant for diffusion flames under normal gravity, so the microgravity environment was used to allow an observation of the effect of the magnetic field on combustion, especially for weak magnetic fields. A steady flame could be sustained with a field intensity larger than a critical value that depends on the O 2 concentration. The critical value was determined experimentally and evaluated with a nondimensional number corresponding to the Grashof number used for gravitational fields. The changes in combustion characteristics, that is, flame shape, length, brightness, and color, were evaluated as a function of the magnetic-field intensity. The flame length decreased with increases in the magnetic-field strength, and the color of the flame shifted from red to yellow, indicating a temperature increase with increases in magnetic-field strength. By evaluating the changes in the flame color with chromaticity treatment, it was concluded that the effect of the magnetic field is dominated by F [O 2 ], where F is the magnetic force acting on the combustion, a function of field strength, and [O 2 ] is the surrounding oxygen concentration.